The invention relates to an electrodeless low-pressure mercury vapor discharge lamp having a closed discharge vessel which contains mercury and rare gas and is provided with a core of magnetic material and with a coil provided around the core, which coil is connected to a high-frequency supply unit, a wall of the discharge vessel situated around the discharge being provided with an interference-suppressing, transparent, electrically conductive layer which can be connected through an electric conductor to one of the two poles of the supply mains.
A lamp of the kind indicated is known from U.S. Pat. No. 4,568,859.
In the known lamp, the core of magnetic material and the surrounding coil are accommodated in a cavity in the discharge vessel. The transparent electrically conducting layer is present on the inside wall of the discharge vessel. The electric conductor connected to the conducting layer is passed to the exterior through the wall of the discharge vessel and connected to one of the poles of the supply mains during lamp operation. It is achieved in this way that high-frequency interferential electric fields outside the lamp are reduced to an acceptable level.
A problem in the known lamp is the lead-through of the electric conductor through the wall of the discharge vessel. Such a lead-through renders the construction of the lamp intricate and expensive. In addition, stresses can easily arise during lamp operation in the glass at the area of the lead-through as a result of differences in the coefficients of expansion of the materials used. The risk of leaks in the discharge vessel is therefore by no means imaginary.